This invention generally relates to a method and to an apparatus for forming a crimped joint and more particularly, to a method and to an apparatus for forming a crimped joint in an electrical wire terminal and which provides reduced electrical contact resistance within the formed joint.
Crimped joints are commonly used in electrical systems, such as automotive electrical systems, in order to selectively and electrically interconnect electrical components. For example and without limitation, crimped joints are used in electrical wire harnesses which electrically interconnect various components or portions of an automobile. Particularly, crimped joints are used to couple electrical connectors or terminals to the ends of the wires in the harness in order to facilitate the connection of the wires to various components, devices or other terminals.
These types of crimped joints are typically formed by use of a die set (e.g., a punch and an anvil) which are selectively used to compress and/or deform a xe2x80x9cbarrelxe2x80x9d portion of the terminal in which the electrical wire resides. Particularly, the electrical wire is placed in the xe2x80x9cbarrelxe2x80x9d portion of the terminal which is subsequently compressed by the die set. As the die set is compressed, two xe2x80x9cwingsxe2x80x9d or flanges which typically form the barrel portion of the terminal are bent downward into the wire bundle. Further compression of the die set further deforms the barrel and tightly packs the strands of the wire bundle together, thereby forming a crimped joint.
While these types of crimped joints are effective to relatively quickly connect terminals to the ends of electrical wires, they suffer from some drawbacks and are generally considered a xe2x80x9cweak linkxe2x80x9d in the wiring harness. For example and without limitation, when compared with other permanent electrical connection methods (e.g., soldering), crimped joints typically show higher initial contact resistance and have a greater tendency to introduce electrical failure within a wiring harness over their respective service lives. One cause of the relatively high contact resistance in these types of crimped joints arises from resistive material (e.g., xe2x80x9coxidesxe2x80x9d) which resides on the outer surfaces of the various strands of the electrical wire and on the inner surfaces of the terminal barrel. The crimping process and die set generate primarily only xe2x80x9cnormalxe2x80x9d type forces between the wire strands which are not effective to remove a significant amount of the resistive material from the wire strands and from the terminal barrel. Furthermore, attempts at removing these resistive materials or oxides prior to forming the crimped joint are excessively costly and/or time consuming.
There is therefore a need for a method and an apparatus for forming a crimped joint which overcomes the previously delineated drawbacks of prior methods and apparatuses and which provides a crimped joint having a reduced amount of contact resistance.
It is a first object of the present invention to provide a method and an apparatus for selectively forming a crimped joint in an electrical wire terminal or connector which overcomes the previously delineated disadvantages of prior automotive electrical interconnection schemes and systems.
It is a second object of the present invention to provide a method and apparatus for forming a crimped joint in an electrical wire terminal or connector which provides a joint having reduced contact resistance.
It is a third object of the present invention to provide a method and an apparatus for forming a crimped joint between an electrical wire and a terminal barrel which automatically causes oxides to be removed from the surfaces of the electrical wire and the terminal barrel, thereby forming a joint with reduced contact resistance.
According to one aspect of the present invention, an apparatus for forming a crimped joint is provided. The apparatus forms a crimped joint between an electrical wire terminal having a first longitudinal axis and a barrel portion having an interior surface, and a wire having an exterior surface which is disposed within the barrel portion and a second longitudinal axis. The apparatus includes a first die member having a first surface which is concave relative to the first and second longitudinal axes; and a second die member having a second surface which is convex relative to the first and second longitudinal axes and which is adapted to selectively engage the barrel portion and to cooperate with the first die member to deform the barrel portion effective to form a crimped joint between the wire and the terminal and to bend the barrel portion and the wire respectively along the first and second longitudinal axes, the longitudinal bending being effective to cause the interior surface of the barrel portion to slide longitudinally relative to the exterior surface of the wire, thereby reducing contact resistance between the barrel portion and the wire.
According to a second aspect of the present invention, a method is provided for forming a crimped joint having reduced contact resistance. The crimped joint is formed between a terminal having a hollow barrel portion with an inner surface and an electrical wire having an outer surface. The method includes the steps of disposing the electrical wire within the hollow barrel portion; deforming the hollow barrel portion effective to compact the barrel portion and the wire, thereby forming the crimped joint; and twisting the barrel portion and the electrical wire about their respective longitudinal axes, effective to cause the inner surface of the barrel portion to slide relative to the outer surface of the electrical wire, thereby reducing the contact resistance within the crimped joint.